John Wesley on John 6:27

Labour not for the meat which perisheth - For bodily food: not for that only not chiefly: not at all, but in subordination to grace, faith, love, the meat which endureth to everlasting life. Labour, work for this; for everlasting life. So our Lord expressly commands, work for life, as well as from life: from a principle of faith and love. Him hath the Father sealed - By this very miracle, as well as by his whole testimony concerning him. See Joh 3:33. Sealing is a mark of the authenticity of a writing.